Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilized in a variety of mechanical applications. For example, PDCs are used in drilling tools (e.g., cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing machinery, and in other mechanical apparatuses.
PDCs have found particular utility as superabrasive cutting elements in rotary drill bits, such as roller-cone drill bits and fixed-cutter drill bits. A PDC cutting element typically includes a superabrasive polycrystalline diamond (“PCD”) layer commonly known as a diamond table or a PCD table. The PCD table is formed and bonded to a cemented tungsten carbide substrate using a high-pressure/high-temperature (“HPHT”) process.
The PDC cutting element may be brazed directly into a preformed pocket, socket, or other receptacle formed in a bit body. The substrate may often be brazed or otherwise joined to an attachment member, such as a cylindrical backing. A rotary drill bit typically includes a number of PDC cutting elements affixed to the bit body. A stud carrying the PDC may also be used as a PDC cutting element when mounted to a bit body of a rotary drill bit by press-fitting, brazing, or otherwise securing the stud into a receptacle formed in the bit body.
The performance of PDCs has been improving over the years as manufacturing technology advances. However, there can be some variability in any manufacturing process that results in varying PDC durability from the same production batch.
Very few non-destructive testing (“NDT”) methods have been effective for testing PDCs. X-ray imaging is not effective due to strong X-ray attenuation of the cemented tungsten carbide substrate. Ultrasonic imaging can achieve high resolution, but the observed features may have little relationship to the properties that the manufacturer would be interested in measuring in the PDC. Eddy current measurements may have low resolution and excessive requirements for sensor positioning precision. Also, the utility of eddy current testing may be limited because the PCD table and substrate of the PDC are often ferromagnetic. Infrared imaging has so far achieved useful contrast only at temperatures high enough to damage the PCD table.